Mammoth Lakes

A VOLCANIC EDGE

Elevation: 7,093 feet

WHAT TO DO IN MAMMOTH LAKES

Some Favorites From Our Expeditions

Do some volcanic sightseeing with touring at Devils Postpile National Monument, Horseshoe Lake and Hot Creek.

Connector.

Keep an eye out for the Smokey the Bear cutout beside the northbound side of Highway 395.

Connector.

Take the short hike to Panorama Dome to see how well you’ve adapted to the altitude and take in another spectacular 360-degree Sierra view.

Geological Intrigue

Besides being a famed ski destination, Mammoth Lakes and the surrounding area is perhaps the best place to understand how the Sierra Nevada continues to change. Geologically young, it’s still growing and being shaped. This is one of the spots where that process is most visible because it is home to eastern California’s volcanic system, which spans from Mammoth Mountain north to the Inyo-Mono Craters and Mono Lake near Lee Vining.

The Long Valley Caldera: Volcanic Collapse

Mammoth Lakes is situated along the ridge of the Long Valley Caldera, one of the largest volcanic depressions of this type in the world and the remains of a volcano far older and more powerful than Mount St. Helens in the Cascades.

Measuring 10 miles long and 20 feet wide, this crater was created 760,000 years ago by what is likely one of the most violent eruptions to occur in North America. The force blasted ash as far as Nebraska and molten rock across much of Eastern California. Once that magma was expelled, the area over where it had flowed below ground collapsed more than a mile into that now empty space.

Enduring Volcanic Stirrings

Following creation of the Long Valley Caldera, eruptions in the area continued for thousands of years. Hulking Mammoth Mountain (a volcano itself) was built by a series of them. Yet the volcanoes eventually quieted, with the most recent eruption near the Sierra Nevada (a small one) occurring in nearby Mono Lake sometime in the 1700s or first half of the 1800s.

Nonetheless, the volcanoes remain active.

Earthquakes

One sign is a history of fairly frequent earthquakes — owing to the combination of pressure from the molten rock moving up toward the earth’s surface and movement along the faults here. What’s more, it appears that this geological restlessness has intensified in the last few decades, with the Long Valley Caldera serving as ground zero.

Earthquake swarms (many in a short period of time) became more regular starting in 1978 and, after a particularly strong one in May of 1980, scientists took a closer look at the Long Valley Caldera. They would discover that its center had risen sharply in less than a year after a long period with no meaningful change. The cause is new magma rising below it and the dome-like swelling has continued. The US Geological Survey (USGS) now monitors the Long Valley Caldera and surrounding area for early signs of potential eruption. One such event that recently drew attention was an earthquake swarm under Mammoth Mountain in early 2014.

A Boiling Swimming Hole: Hot Creek

Besides earthquakes, there are several other more visible signs that the volcanos here are far from inactive. Hot springs in the Sierra’s volcanic region — not to mention geothermal power plants — are fed with water heated by magma flowing beneath the ground. Boiling water and geysers bubble in Hot Creek. (Once popular with swimmers, it was closed off in 2006 because the unpredictable, scalding water was deemed too dangerous.)

A Creepy Dying Forest: Horseshoe Lake

In a place with so many fascinatingly strange sights, Horseshoe Lake stands out as one of the most peculiar. After scientists began studying the Long Valley Caldera and Mammoth Mountain more carefully, they also discovered high levels of carbon monoxide were seeping into the soil from below and killing large areas of trees.

This is shown to dramatic effect at Horseshoe Lake where the graveyard that remains is reminiscent of a burned-out forest. But it’s even more eerie. Danger signs noting the hazard carbon monoxide poses to humans are posted throughout.

Lava Gone Cold: Devils Postpile

Devils Postpile offers a rare glimpse of what happens to lava as it cools. It is the remnants of a basalt lava flow that moved through Reds Meadow Valley 100,000 years ago or perhaps even more recently, and what makes it particularly unique is that it shows the flow’s interior. (A glacier moving through here years later exposed it.)

Basalt lava is hotter than other types, allowing it to move quickly, and it did so here until it became blocked by some sort of natural dam. It then pooled into a lake that was as deep as 400 feet in some spots. As it cooled, the lava contracted and cracked. The result are the unusual hexagon-shaped columns that stand together stretching vertically to a height of about 60 feet.

It is a national monument, making it part of the National Park System. (It was once part of Yosemite, before the boundary was revised to exclude areas near Mammoth Lakes in 1905 after pressure from the mining industry.) For those who want to pay a visit, Devils Postpile is accessible in summer only, and getting there involves a shuttle bus.

The Escape Route: Mammoth Scenic Loop

Today, a road outside of Mammoth Lakes called the Mammoth Scenic Loop is seemingly a route for a leisurely drive, but it originated after that 1980 earthquake swarm. The intent was to provide an additional access to Highway 395 in the event that evacuation would be necessary at some point.

A 12th Sierra Pass Stopped by Ronald Reagan

Though Mammoth Lakes lies at a high altitude, the terrain into the backcountry of the Sierra from here is somewhat less punishing than the rest of the stretch between the Tioga Pass into Yosemite and the Sherman Pass to the south. During the Gold Rush, the gap in the mountains here was a widely used trans-Sierra route called the French Trail, so popular that it was one of the toll roads that emerged during this time.

In 1972, there were in fact plans for a highway crossing the Minaret Summit. When the 1964 Wilderness Act was passed (allowing land to be designated as wilderness in which roads, vehicles and permanent structures are prohibited), this land had been left out so that a trans-Sierra pass would remain a possibility.

The person who put a stop to it was Ronald Reagan, who did not have a reputation as a keen environmentalist during his presidency. Yet when he was governor of California, he convinced President Nixon to abandon plans for a pass here (as work was set to get underway). He did so in dramatic fashion, taking a trip by horse into the Sierra and announcing a proposal to combine the John Muir and Minarets Wilderness Areas. The move secured the Sierra Nevada as home to the longest stretch of wilderness area in the lower 48 states.

Mammoth’s Lush Landscape: The East Side Oddity

The gapping in the mountains here is also why Mammoth Lakes (as well as neighboring June Lake) has a more traditionally green alpine look compared to much of the East Side.

At this lower point in the Sierra Crest, weather patterns moving across the mountains lose less of their moisture, allowing for more rain to fall and — most notable for this ski mecca — snow.

Mammoth is one of the snowiest spots in California, and the fencing seen along Highway 395 here are snow fences to keep blowing flurries from accumulating on the road.

High Altitude = Prime Athletic Training Ground

Mammoth Lakes is the highest altitude of the major East Side towns. The thinner air here can cause some discomfort when first arriving (headaches, shortness of breath), but it also provides an appealing training ground for committed endurance athletes.

Much study has been devoted to altitude training (especially as runners who live and train at higher elevations have come to dominate the Olympic medals race). The idea is that as the body adapts to less oxygen in the air, it produces more red blood cells to bring oxygen to muscles. The higher red blood cell count is sustained for a time, thus providing a competitive advantage in lower-elevation events.

Elite runners preparing for the Olympics, marathons and other events now consider Mammoth Lakes to be an optimal training ground because the high altitude combines with stunning scenery.

More Mal-Adjusted Bears

As in Tahoe, bears have generated more headlines in Mammoth Lakes recently as mild winters have diminished their natural food supply and interfered with their hibernation patterns. One of the more brazen bruins wandered into a supermarket in the fall of 2013 to help itself to some apples.

The town even has its own bear specialist, Steve Searles. He’s known as “The Bear Whisperer.” Self-taught, he has also worked with Yosemite and helps bears and humans to better coexist by shooing bears from homes and other populated areas and training people so that bears are less attracted to civilization.